A wafer is etched using a plasma system. A wafer is a substrate that is made of a semiconductor material and used in electronics to manufacture integrated circuits. A variety of operations, e.g., etching, doping, ion implantation, deposition, photolithographic patterning, etc., are performed on the wafer to form integrated circuits on the wafer. The integrated circuits are then diced and packaged.
Current high aspect ratio (HAR) contact etch technology, e.g., HAR>50:1, etc., uses significantly low radio frequency (RF) signals to produce high energy ions. However, the high ion energy leads to significant mask loss.
Also, pulsed plasmas are typically used for better mask selectivity with low and high power plasma energy regimes to deposit polymer and to etch contact. The polymer is deposited using a low amount of power and the contact is etched using a high amount of power. However, most of the mask is lost during the high power pulse, e.g., when 2 megahertz (MHz) plasma produces none or small amount of low energy ions, etc.
It is in this context that embodiments described in the present disclosure arise.